Makeups play an important role in correction of skin blemishes and emphasis of eyes and lips, making the appearance look beautiful. Among the components mixed in makeup cosmetics, coloring materials are used to conceal stains or marks, allowing the skin to look healthy and be tinted with fascinating tones. The coloring materials used in these cosmetics are divided into organic synthetic coloring agents, natural colors, and inorganic pigments.
The organic synthetic coloring agents are classified into a dye, lake, and an organic pigment. The dye is a compound which is dissolved in water, oil, and alcohol, and contains an azo group and the like as a chromophore group, and the lake is a type of an insoluble metal salt bound to a water-soluble dye. The natural colors are extracted from plants, animals, and microorganisms. In this case, such materials have been used as additive materials in foods for a long time because the materials produce poor colors, compared to the synthetic coloring agents. In recent years, the natural colors have again come into the spotlight as the natural colors are used for medicines requiring the safety.
The inorganic pigments are classified into coloring pigments, white pigments, extender pigments, and pearlescent pigments. The coloring pigments give colors to cosmetics, and the white pigments serves to regulate skin covering power. The extender pigments serve to adjust tones as diluents for coloring pigments and play a great role in senses of feeling in use, such as spreadability, adhesion, etc., of products, and formulation of the products. Also, the pearlescent pigments are pigments that endow colors with pearly luster and have a special optical effect, which are used to give an iris color or a metallic luster.
The extender pigments included in conventional cosmetics include talc, kaolin, silica, talc, sericite, calcium carbonate, magnesium carbonate, a silicic acid anhydride, etc., and serve to adjust the depth of color and control spreadability and feeling of formulations, etc. The white pigments include titanium dioxide, zinc oxide, etc. In general, kaolin, talc, silica, and titanium dioxide are basic components of the cosmetics as powders having white color while maintaining applicability, adhesion and skin covering power.
The powders used in the makeup cosmetics require adhesion, hiding power, applicability, spreadability, moisture absorbency, oil absorbency, and skin friendliness, and may be obtained by mixing or applying two or more powders. For example, the inorganic pigments such as titanium dioxide exhibit excellent adhesion, hiding power, etc., but have poor senses of feeling in use such as applicability, spreadability, etc. To make up for these drawbacks, there are known techniques for preparing cosmetics using good hiding power and difference in optical refractive index by coating titanium dioxide with silica at a predetermined ratio to prepare an inorganic composite powder.
However, the conventional coated inorganic composite powder as described above do not exhibit satisfactory characteristics such as stability, adhesion, a sense of feeling in use, and sustainability at the skin and external conditions when actually applied onto the skin.
To solve these drawbacks, methods of performing water repellency treatment using surface treating agents such as silicon compounds, fluorine compounds, metallic soaps, higher alcohols, fatty acids, metal salts of amino acids, lecithin, and the like have been proposed in the related art. Among theses, a surface treatment method using silicon compounds or metal salts of amino acids is common. In recent years, a surface treatment method using a combination of the two methods has been proposed.
Meanwhile, the coated powder whose surface is treated with a fatty acid, a metallic soap, and a metal salt has good adhesion to the skin and a good sense of feeling in use on the skin, but has poorer water resistance than the powder surface-treated with the silicon compound and exhibits insufficient spreadability due to somewhat a rough sense of feeling when applied onto the skin. Also, because the metal salt is absorbed onto a surface of the powder in the form of fine particles, the metal salt may be detached due to poor stability in a surface-modified state. In addition, the coated powder still has problems regarding degraded color reproduction when used together with other silicon raw materials.